US2616848A - Sewage treatment - Google Patents

Description

Nov. 4, 1952 l.. B.- GRIFFITH 2,616,848

sEwAGE TREATMENT Filed oct. 17, 1947 2 sHEETs`sHEET 1 Inventor:

ls orney FIGLI L. B. GRIFFITH SEWAGE TREATMENT Nov. 4, 1952 2 SHEETS-SHEET 2 Filed Oct. 17, 1947 mm w n# i m f .I m6 f A B .m n h /v e W Mv. L

y B 3 m F the incoming raw sewage.

Patented Nov. 4, 1952 `'UNITED STATES PATENT a OFFICE I sew-.Acre TREATMENT, Llewellyn ,Brooks Grinch, austin, "mex, .Application october 17, 15.947, semina-180546 I (c1. 21o-zi l Claim.

This.invention .relates to sewage treatmentend has for its principal object the'provision ol? a simple and .enicient unit particularly suitable for wery small installations.

An important `feature ci myinvention is the placing of. va contact aerator `over .the primary tank sludge hopper this having the effect of permitting the carrying on of the primary and .secondary actions in a single tank thus lessening the load :on the second stage as well as making .for greater veconomy by the consequent vsaving .of piping, solenoid `valves and clock mecha- .An important object of the invetnion is to arrange both :the primary settling and the bio- 'logicai .secondary treatment so they can :be placed in a single tank. This increases the settling `tank eciency and thereby reduces the amount lof uwork to be accomplished .by the more vexpensive biological methods. In such a manner the solids from the primary treatment and the secondary treatment can .both easily be removed from a combined sludge hopper by a single sludge removal lline operate-d automatically.

vFurther objects of the invention are 'to provide systems ci sewage treatment in which the Aeiici'ency of the -primary treatment is increased by causing noos to carry down with them extrernely small `:particles of soiid matter: to operate the primary and secondary treatments in ar single tank .and to` `prevent the settling conditions from becoming toxic and thereby .injuring the healthful sewage organisms clinging to the separator plates or contact surfaces.`

Still anotherv object lof the invention is to .provide an improved sewage treatment'method which includes a single chamber wherein primary settling of the raw sewage is accomplished plates or other suitable surfaces in suchlfashio'n that-the liquid is constantly recycled-through the plates many timesbefore it 'sjpillsfi.v over a lweir into a second' stage at-the rate ciflcw of win gravitate to the Vmopperen bottom of the tank and will 'loe4 drawn olf in spaced and very 'short periods, at intervals of lfrom one to live hours. 'The lighter solids, which in an ordinary settling tank would spili vover the Weir, are con- .sequentlycaught by the flocs passing downwardly l 'through the secondary treatment unit and thus these, smaller solids will 'be carried down to the same hoppered bottom of the same tank. All .settled solids rapidly become septic and. if the putrefaction cycle continues without loxygenation vtoxic liquids are formed which are extremely diicult to treat by aerobic biological methods.

`.For-tunately the septic sludge forros gas bubbles which `'cause the sludge to rise in large masses and in the apparatus of the present .invention .these rising .masses of sludge ,pass through the streams of air from the air diiusers which .break vup the sludge masses, release the gas bubbles Ianch fof course, likewise to lessen the load on the second stage which, in turn, consists of a settling tank having a .nal biological treatment stage which feeds to the `discharge opening or pipe through `a Iilter which .mats itself with algae (as in nature) and is, therefore, a true biological lter.

,As wiil -be noted from the above, there will be no. rlslulkngnr burning .of the septic lsludge `:from the iirstv chamber into the second .chamber because the airin the rst chamber breaks up the: sludge and throws .it-,to the bottom of the tank where it is removed mixed with the heavier and .quicker .settling .material so there will be no formation. 'ofY toxic liquids.

In the drawings, .Figure 1 is a. plan view of a device employ 'ing-my invention..

Figure 2 is a vertical section taken on vline V2`-2 of Figure 1.

Figure. 3 is a vertical section approximately at right angles to Figure 2 and taken on Vline Spy-3. 1Iof Figure 2.

.Referring primarily to the plan view, Figure 1, my .device includes va 'tank l, providing a dgester `chamber il, generally of conventional type :and .separated by aflieat transfer common 4l2 from la. sewage treatment unit consistv ing-"cfa nrst chamber I4 and a second chamber @wise secured to 'each plate.

l5, separated by a wall I6 having at its top a weir I'I over which the liquid flows from chamber I4 to chamber I5 over the top of weir II in accordance with entry of material through the entrance pipe I8. To the left of tank I5 is a sludge drying bed I9 of any conventional type.

While my device may have a sieve of any type and a baille near the point of discharge of the pipe I8 into chamber I4, I find that I can readily omit these two well-known items and discharge directly into the settling tank which is the chamber I4. The sewage reaching this settling tank slowly settles its larger solids which fall to the hoppered bottom 2|] from whence they are drawn at intervals of about one, two, three or four hours, depending upon the amount and septicity of the sludge, through a lift or air pump 2| which discharges thru a horizontal pipe 22 to an air vent 23 of well-known form. The settling tank I4 discharges over wier I'I to the second stage treatment tank I5. l.

An air pump 25 in the second stage tank I5 operates consecutively with air pump 2| both being about the same size which would be say 4". The plant illustrated with the digester is roughly 8' x 8 x 8 in size but the invention contemplates sizes of from 40 persons up to'plants for thousands. 'The air pump 25 discharges thru a horizontal pipe 26 to a spray-head 21, the net result'being that the slight amounts of .solids A preferred method would be to operate the'air lift 25 for say 15 minutes andthen after giving' the material an hour and a half or more time to resettle in the sludge hopper of the primary settling tank so that all the solids from the plant are concentrated into one hopper. These solids are withdrawn thru the air lift 2| and discharged into the sludge digestion tank II. As will be understood, the pump 2| would only work for a minute or so as it is highly desirable that the amount of liquid taken from the settling tank to the digester be at a minimum while taking as great a part of the solids as is possible.A

Referring particularly to Figure 3, supporting ledges 28 are provided on two opposite walls of the tank I4. rIhese ledges may readily be single two by fours. extends well above the water level 3|, as indicated at 32, and is caulked along the vertical edge. Between the permanent baiiie 30 and the'wall I6 dividing the chambers I4 and I5 I arrange a plurality of contact plates 33 which in an installation of this size would be say 4' ft. square and spaced apart about an inch. The plates 33 can be any shape or of any material such as aluminum, wall-board or any material that provides passage of the sewage and has a surface to which the aerobic sewage organisms will cling. The plates are separated by spacers 34nailed or other- Consequently any plate can be removed witho1.1't.disturbing the Others.

Under all of the plates but slightly above the bottom of baille 3U I arrange two porous air diffuser tubes 35 which receive air through vertical pipes 33 and header 3'|.which receive their air supply from a blower; :39, drivennby a i" relatively small motor 40.- The air blower-39 furnishes all of the air for the system and altho it furnishes air constantly to the diffuser tubes which feed the air almost entirely in an upward direction, this supply is constant whereas the air At the influent end the baiiie 3D supplied to the pumps 2| and 25 is supplied only intermittently. Consequently I employ for each of the air lifts a clock-operated solenoid valve 4I for control of the air pump 25 and a similar device 42 for control of the air lift 2| in the settling tank I4.

When no air is being used the normal flow of the sewage from the bottom of the contact aeration plates to the top would take` place in about twenty minutes but when the air diffusers increase, the upward velocity causes the sewage to rise from the air diiusers to the level of the liquid in about four seconds time. Inasmuch as liquid can not move from the tank I4 to the tank I5 at any rate other than at the rate of flow of the volume of the new material added through pipe I8, this quick raising of the material in the biological contact aerator cell causes a rapid up and down cycling of the sewage between the several surfaces at a rate about 300 times faster than if there were no air-propelling effect from the air dffusers.

As this material descends between the surfaces in this secondary treatment unit it carries with it a .biological floc which forms a blanket below the unit at the depth of the bottom of baiiie 30 where the descending solids are coming from the initial settling, and since thisA material is flocculent and aerated it entraps or attaches to itself the very lne solids which do not readily settle by gravity and in this way settle many small solids which would not ordinarily settle at all. By taking out these extremely ne solids we minimize the organic load on the biota in the aerator. Expressed in other words, these solids which are already septic or which will soon become septic are settled out and can be removed to the sludge digester; otherwise they would impose an additional load on the subsequent biological treatment. This removal of normally unsettleable solids of course greatly increases the efficiency of the treatment plant.

- The material passing over wier I'I from chamber I4 to chamber I5 settles in the latter and vwhatever solids there may be fall to the bottom 44 of tank I5 and are drawn, as previously explained, upwardly through the air pump 25 and discharged through the spray-head 2'I on the top of liquid in tank I4 which periodically agitates the surface of the liquid in tank I4 and in this way breaks up any masses of sludge or scum which have become gaseous so that it will release the gas bubbles and permit it to resettle to the bottom 20.

The biologicaltreatment unit 46 in tank I5 to the right of Figure 3 is identical with the similar unit in the secondary unit in tank I4 with the exception that it is not necessary to place it immediately over the hopper bottom due to the normal aerobic conditions in I 4 and the fact that considerable aerobic floc is carried over the wier from the first aerator. On top of this unit I place a quarter inch mesh wire screen between the tops of plates 33 and the water level 3|. This screen 48 acts as a natural biological filter because its size is such that it collects the algee which mat and form a. highly eiiicient lter returning undesirable constituents to the biological treatment unit and allowing only the relatively pure water to pass to the discharge chanel 49 and the exit The operation of my device is as follows, re-

l; ferring particularly to Figure 3: The raw sewage the hoppered bottom to a point directly under the secondary stage. The secondary vtreatment unit has a liquid Volume suiilcient to provide an average detention period of from to 60 minutes, depending on the spacing of the biological surfaces. Air is provided below the Contact surfaces in amounts surllcient to oxygenate the liquid in the aeratcr to not less than about two parts per million of dissolved oxygen or adequate amount for sustaining active aero-bic life. The upward and downward flow of sewage between the biological surfaces not only greatly increases the intimate contact period between the liquid and the biological organisms, but agitates the growth in such manner that it is able to spread out from the plates in a horizontal direction. The continuous unloading of the slimes and biological growth causes a floc to be formed. As these locs settle downward they entrap with them many small organic solids which otherwise would not settle at all. When the masses of solids settle in chamber I4 and are carried to the right, as seen in Figure 3, they become septic after a few hours and undergo anaerobic decomposition. This results in the formation of gases and if allowed to continue long enoughl would result in the formation of toxic liquids which are extremely diflicult to treat by the ordinary aerobic biological methods. When this septic gas first forms, large masses of septic sludge in the hopper bottom are carried upward by the entrapped gas bubbles but since the at or horizontal hopper bottom is directly below the secondary stage, these rising masses are aerated and agitated as they are rapidly carried upward. In this way the gas bubbles are released and the septic solids are blanketed with the settling aerobic noos and are returned to the hopper bottom before the anarobic action has progressed far enough for the extremely septic liquids to become toxic and hence detrimental to all forms of aerobic biological treatment.

Material passing over the wier I1 in the center of the ligure at the top pass to the second stage and what slight amounts of solids do pass over are lifted from time to time by the airpipe 25 and returned to the primary settling chamber I4.

The eiiluent after passing through the biological treatment unit 45 is discharged through channel i3 at the right of the iigure.

in the claim a biological treatment unit is intended to cover a unit in the path of the sewage including appropriate organisms in an environment suitable for their functioning to the end that they may purify the sewage. The environment would necessarily include surfaces to which the organisms might cling and the presence of oxygen.

What I claim is:

In a sewage treatment plant, a tank having arailel walls, a middle partition extending from .ine tank wall to the opposite parallel wall to ivide the tank into a digester chamber on one ide of the partition and a raw sewage treatment chamber on the opposite side of the partition, the entire length of the partition being in contact with raw sewage on one side and the entire length of the partition being in contact with the digester chamber on the other side, said partition being of such thickness and material as readily to transfer heat from the warmer incoming sewage to the cooler digesting sludge, whereby anaerobic action in igester chamber is speeded up.

LLEWELLYN BROOKS GRIFFITH.

REFERENCES CITED The following references are of record in the file ci' this patent:

UNITED STATES PATENTS Number Name Date 1,139,024 Frank May 11, 1915 1,399,561 Imhoif et al Dec. 6, 1921 1,642,206 Imhoff Sept. 13, 1927 1,700,723 Imhoff Jan. 29, 1929 1,717,780 Imhoi June 18, 1929 1,893,623 Imhoff Jan. 10, 1933 2,008,507 Laughlin July 16, 1935 2,348,125 Green May 2, 1944 2,389,357 Griith Nov. 20, 1945 2,413,838 Mallory Jan. 7, 1947 2,427,886 Walker Sept. 23, 1947 2,458,163 Hays Jan. 4, 1949

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